属性基加密因其细粒度访问控制在云存储中得到广泛应用.但原始属性基加密方案中单授权机构带来了分发私钥的计算瓶颈与信任问题.为解决上述问题,该文基于素数阶双线性群构造了一种分布式属性基加密方案,方案中授权机构由多个权威中心和多个属性中心组成.权威中心负责系统建立及用户身份相关密钥生成,且每次用户私钥申请过程中只需一个权威中心参与工作,采用多权威中心的目的是提高系统的稳定性和降低权威中心的计算量;属性中心负责不同的属性域,相互独立甚至不需要知道其它属性中心的存在.同时,该方案的密文长度与属性数量无关,为一个常值;在解密运算过程中需要的对运算与属性数量也无关,为2个对运算.该文基于q-Bilinear Diffie-Hellman Exponent假设在随机预言机模型下对方案进行了选择明文攻击的安全性证明.最后从理论和实验两方面对所提方案的功能与效率进行了分析与验证.实验结果表明所提方案具有固定密文长度和快速解密的能力,大大减少了存储负担并提高了系统效率.%Attribute-Based Encryption (ABE) scheme is widely used in the cloud storage due to its fine-grained access control. However, the single authority can lead to the trust issue and the computation bottleneck of distributing private keys in the original ABE schemes. To solve these problems, a distributed ABE scheme that consists of a number of central authorities and multiple attribute authorities, is constructed based on the prime-order bilinear group in this paper. Here, the central authority is responsible for establishing the system and generating the private key for the user, and a single private key is generated by only one central authority. In order to improve the stability of the system and reduce the calculation of the center authority, a plenty of central authorities are adopted. The attribute authority, which is independent of each other, is responsible for managing different attribute domains. At the same time, the ciphertext length of the proposed scheme has nothing to do with the number of attributes, therefore, it is a constant. The most important thing is that the decryption computation needs only two bilinear pair operations. The scheme is proved selectively secure based on q-Bilinear Diffie-Hellman Exponent (q-BDHE) assumption in the random oracle model. Finally, the functionality and efficiency of the proposed scheme are analyzed and verified. The experimental results show that the proposed scheme has both constant-size ciphertext and the ability of fast decryption, which greatly reduces the storage burden and improves the system efficiency.
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